It is well-known that various simple carbides can be used to produce fuel gases such as acetylene, methane, allylene, etc., and that calcium carbide manufacture and conversion to acetylene has provided the basis for a major industry for many years. Nevertheless, carbide-acetylene has never had a measurable impact on the production of general purpose fuels. Rather, its applications have been restricted to providing high energy fuel for the welding gas industry plus major non-fuel or chemical applications, for example, as a chemical intermediate. Several factors have precluded more widespread use of calcium carbide derived acetylene for general fuel purposes; among these are: (1) High input power requirements resulting from the necessity of employing electric arc furnaces to reach the temperatures needed to manufacture calcium carbide (approximately 2000.degree. C.); (2) The hazards of handling the derived acetylene, either under pressure or in mixtures with air, due to its endothermic nature; (3) The magnitude of the disposal problem for the spent lime that would arise if large amounts of carbide acetylene were used for general fuel purposes; (4) Transportation costs of raw materials and calcium carbide occasioned by high total tonnages per unit fuel value; and (5) Total system costs in comparison with alternative fuel systems.
Patents and a literature article bearing upon the state of the art of manufacture or reaction of carbides or generation of combustible volatiles of the type contemplated in the present invention includes the following:
U.S. Pat. No. 2,802,723--Aug. 13, 1957
U.S. Pat. No. 3,031,287--Apr. 24, 1962
U.S. Pat. No. 3,154,378--Oct. 27, 1964
U.S. Pat. No. 3,201,052--Aug. 17, 1965
U.S. Pat. No. 1,735,925--Nov. 19, 1929
U.S. Pat. No. 1,741,307--Dec. 31, 1929
U.S. Pat. No. 1,824,896--Sep. 29, 1931
U.S. Pat. No. 2,445,796--July 27, 1948
U.S. Pat. No. 2,942,959--June 28, 1960
U.S. Pat. No. 3,771,259--Nov. 13, 1973
U.S. Pat. No. 3,405,068--Oct. 8, 1968
U.S. Pat. No. 889,124--May 26, 1908
U.S. Pat. No. 1,445,644--Feb. 20, 1923
U.S. Pat. No. 260,954--July 11, 1882
U.S. Pat. No. 3,115,394--Dec. 24, 1963
U.S. Pat. No. 2,781,248--Feb. 12, 1957
U.S. Pat. No. 2,654,661--Oct. 6, 1953
U.S. Pat. No. 1,173,417--Feb. 29, 1916
U.S. Pat. No. 1,938,202--Dec. 5, 1933
U.S. Pat. No. 1,960,886--May 29, 1934
U.S. Pat. No. 3,188,179--June 8, 1965
U.S. Pat. No. 3,108,857--Oct. 29, 1963
U.S. Pat. No. 2,602,019--July 1, 1952.
Journal of Phys. Chem.-Vol. 65, pp. 2026-2028 (1961).
While the principal volatile products of conversion of carbide "fuel precursors" are hydrocarbons, they may be accompanied by various lesser amounts of hydrogen, carbon monoxide, carbon dioxide and compounds containing carbon, hydrogen and oxygen (and/or additional elements). In the succeeding discussion, the term "fuel" shall refer to all such volatiles, and "fuel precursor" shall designate a compound capable of generating all such volatiles where used for fuel or non-fuel purposes.
It is therefore a primary object of the present invention to provide a process for the economical production of fuel precursors and for the conversion of the fuel precursors to hydrocarbon gases or liquids for various fuel or non-fuel uses.
It is another object of the invention to provide a method of producing a fuel gas compound or mixture of greater intrinsic stability and safety than acetylene, for example, a fuel gas consisting primarily of methane or comparable compounds.
Another further object of the present invention is to provide a process for the manufacture of fuel precursors, which process uses substantially less power per unit derived fuel energy than the calcium carbide-acetylene system, which can be operated at substantially lower temperatures, and for which the mineral residue (oxide-hydroxide) generated from the fuel gas conversion stage can be readily and economically recycled to manufacture more fuel precursor.
Still another object of the present invention is to provide a fuel precursor which may be stored or stockpiled safely without undue fire hazard or deterioration due to air exposure or other factors, to provide an economical reserve capacity for accommodating short term or seasonal fluctuations in fuel demand or supply requirements during scheduled or unscheduled interruptions in manufacture of fuel precursor.
Yet another object of this invention is to provide a continuous process for the manufacture of fuel precursor and a conversion process for hydrocarbon generation which may be rapidly adjusted to meet utility demand loads.
A further object of the invention is to provide mineral carbide fuel precursors which are convertible to fuel gases or liquids.
Yet a further object of the present invention to provide fuel precursors from which sulfur and other noxious or undesirable impurities introduced by the coal or other raw materials during manufacture of the precursors can be substantially reduced or removed easily to provide environmentally clean gaseous or liquid fuels.
Even another object of the invention is to provide fuel precursors capable of generating high yields of unsaturated hydrocarbons, such as olefins and acetylenes, which are useful for manufacture of polymers and other valuable chemical products.
These together with other objects and advantages which will become subsequently apparent reside in the details of the process and operation of the invention as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.